What is it?

Debuted on the S-Class hybrid and now available on the C-Class Hybrid, Mercedes-Benz has developed a system designed to take full advantage of topography for charging and discharging a battery through energy recuperation.

The claims

Hybrid vehicles feature an electric motor, used to either provide extra power to the petrol engine to reduce load and fuel consumption or to drive using only battery power. This motor is also used as a generator while decelerating, using the turning force of the wheels to put power back into the battery.

But this system can be inefficient. Arriving at a long downhill section with a fully charged battery wastes an opportunity to recuperate energy through the motor-generator, so Mercedes-Benz has designed a system which allows its hybrids to charge and discharge intelligently.  

How does it work?

Using data stored in the COMAND Online navigation system, the car is able to analyse the topography for 4.4 miles of the road ahead, broken into a grid of one-metre squares, and identify how much energy can be recuperated. The system is always active, and can make intelligent assumptions about where the vehicle is headed even if the driver doesn’t have a route set in the navigation.

This data is then combined with information about the vehicle weight and the behaviour of the driver, such as how heavily they are braking and how fast they are travelling, plus the additional load from auxiliary systems in the cabin, and sent to the hybrid system’s Central Powertrain Controller.

Knowing how much energy can be recuperated in the near future means the drivetrain can choose to discharge the battery by using the motor to assist the petrol or diesel engine. This reduces the load on the engine and saves fuel, but also means the battery has enough capacity to fully recharge when it reaches a downhill stretch of road.

Routes where large amounts of energy can be recuperated are highlighted in green.

The results

Mercedes-Benz says the system was developed to mirror strategic energy use from the new generation of hybrid Formula 1 cars. These are reliant on the 160bhp power increase offered by a battery-powered electric motor under heavy acceleration, so have to pre-plan stretches of recuperation to recharge the battery and stay competitive.

The manufacturer’s Formula 1 hybrid drivetrain has taken eight of the nine podium places for the first three races of 2014 and, for road cars, more efficient energy use should help real-world economy without the extra cost of larger batteries.